The simplest types of centrifugal pump construction have an inlet opening at the rotor suction opening and thus on the projected axis of the pump, whilst the outlet connector leaves the spiral housing tangentially. This arrangement leads not only to a right-angle deflection of the delivery stream but also to an offset between the inlet and outlet lines with respect to one another. A modified design is formed by spiral housings in which the inlet and the outlet lines are located in the same plane in which the axis of the pump is also located. In particular in the case of heating pumps, in-line embodiments are customary in which the inlet and outlet connectors are located opposite to one another and extend perpendicularly to the pump axis. The disadvantage of this embodiment lies in the fact that the distance between the connectors is comparatively great.
The centrifugal pumps with sealed shafts and splitcage motor pumps are joined by a third variant, centrifugal pumps which are driven through a pole ring which is hermetically isolated via a spherical isolating wall from the drive device, a stator or a circulating magnetic ring. The rotors of such pumps no longer have any shafts but form a unit with a pole ring with a spherical surface and are supported only by a sphere and a spherical pan. These supports are particularly well suited for pumps having a vertical axis since the supporting bearing of the whole periphery is then uniformly loaded.